Large rolling bearings which are suitable for the main bearing arrangement of the rotor shaft of a wind power installation, or else for rotary table bearing arrangements in machine tools, are usually produced as ready-to-install bearing units for combined loadings with high demands on running precision, and are designed either as axial-radial bearings or as axial-angular-contact ball bearings depending on rotational speed and duty cycle. Both bearing types absorb radial and axial loads on both sides and also tilting moments, and are preloaded radially and axially without play. While axial-radial bearings are used predominantly in standard applications with low rotational speeds and are generally distinguished by a higher friction torque which increases with rotational speed, axial-angular-contact ball bearings are very well suited to applications involving high rotational speeds, and are distinguished by distinctly low friction and low lubricant consumption.
Large rolling bearings of said type are known inter alia from the applicant's catalog “Wälzlager” [“Rolling bearings”] from January 2006 and are described in the stated embodiments as axial-radial bearings and as axial-angular-contact ball bearings, for example on pages 990 to 1019.
Here, the axial-angular-contact ball bearings shown are composed substantially of a single-part or two-part inner bearing ring and an outer bearing ring and of a multiplicity of bearing balls arranged adjacent to one another in two rows which are inclined in relation to one another, which bearing balls roll with a defined pressure angle with their running surfaces on a plurality of raceways arranged adjacent to one another on the outer side of the inner bearing ring and on the inner side of the outer bearing ring.
In contrast, the axial-radial bearings illustrated are composed substantially of a vertically-arranged circular-ring-shaped outer disk, an inner ring arranged coaxially with respect to said outer disk, as well as two circular-ring-shaped shaft disks arranged axially adjacent to the outer disk on both sides, with one row of rolling bodies each, held at uniform intervals by one bearing cage each and designed as bearing needles or cylindrical rollers, rolling between the two shaft disks and the outer disk and forming a first and a second rolling bearing for absorbing axial forces. Furthermore, another row of rolling bodies, usually held at uniform intervals by another bearing cage and likewise designed as bearing needles or cylindrical rollers, is arranged between the outer disk and the inner ring, which row finally forms a third rolling bearing for absorbing radial forces.
Furthermore, rotary table bearings designed as double-row angular-contact roller bearings are also known in which, as rolling bodies, use is made of two rows of cylindrical rollers which are inclined in relation to one another instead of two rows of bearing balls.
A disadvantage of said axial-radial bearings has however proven to be that the rolling bodies designed as bearing needles or cylinder rollers, in the two rolling bearings for absorbing axial forces have unfavorable kinematics, since said rolling bodies are arranged with their end sides on different pitch circles on account of their axial arrangement, and thereby seek to roll at different rotational speeds on their raceways at said end sides. However, since this is naturally not possible and the rolling bodies are also guided only by their bearing cages, skew or permanent tilting movements of the bearing needles or cylindrical rollers in their cage pockets occurs, as a result of which tilting movements, high constraining forces act on the bearing cages, and which tilting movements cause a relatively high friction moment and an increased generation of heat in the bearing. Here, the generation of heat in the bearing and/or the constraining forces on the bearing cages may briefly become so high as to result in either overheating and inadequate lubrication or in breakage of the bearing cages as a result of overloading, which in both cases leads to premature failure of the axial-radial bearing. Such unfavorable kinematics may duly be eliminated by using the described axial-angular-contact ball bearings with bearing balls, which naturally have more expedient kinematics, instead of the likewise described axial-radial bearings with cylindrical rollers, but such axial-angular-contact ball bearings generally do not have the required load capacity to be able to withstand extremely high forces prevailing, for example, in the main bearing arrangement of a rotor shaft of a wind power installation.